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a SIGSEGV in Linux

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  • S sjlee

    Hello,

    I have a SIGSEGV crash in Qt. Could you please tell me what the crash is? Thanks in advance.

    Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f070370c9f6 in __run_exit_handlers (status=1, 
    listp=0x7f07038ae718 <__exit_funcs>, 
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true)
    at exit.c:77
77	exit.c: No such file or directory.
[Current thread is 1 (Thread 0x7f070281e700 (LWP 4848))]
(gdb) 
(gdb) 
(gdb) bt
#0  0x00007f070370c9f6 in __run_exit_handlers (status=1, 
    listp=0x7f07038ae718 <__exit_funcs>, 
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true)
    at exit.c:77
#1  0x00007f070370cbe0 in __GI_exit (status=<optimized out>) at exit.c:139
#2  0x00007f0700aca371 in QXcbConnection::processXcbEvents(QFlags<QEventLoop::ProcessEventsFlag>) [clone .cold] () from /usr/local/bin/across/libQt5XcbQpa.so.5
#3  0x00007f0700af8de3 in xcbSourceDispatch(_GSource*, int (*)(void*), void*)
    () from /usr/local/bin/across/libQt5XcbQpa.so.5
#4  0x00007f07031b417d in g_main_context_dispatch ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5  0x00007f07031b4400 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#6  0x00007f07031b44a3 in g_main_context_iteration ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#7  0x00007f07043522fe in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/local/bin/across/libQt5Core.so.5
#8  0x00007f07042fd20b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/local/bin/across/libQt5Core.so.5
#9  0x00007f0704304ade in QCoreApplication::exec() ()
   from /usr/local/bin/across/libQt5Core.so.5
#10 0x000000000056adf9 in Across::RunCommonRoutine(int&, char**, _ACROSS_CONTEXT*, __sigset_t const*, int&)::{lambda()#3}::operator()() const ()
#11 0x00007f0703ce9240 in std::execute_native_thread_routine (__p=0x1690b70)
--Type <RET> for more, q to quit, c to continue without paging--
   /var/tmp/sayongza/gcc-9.3.0_source/gcc-9.3.0/libstdc++-v3/src/c++11/thread.cc:80
#12 0x00007f070404d609 in start_thread (arg=<optimized out>) at pthread_create.c:477
#13 0x00007f07037e5293 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

    The backtrace is for Qt5.14.2 and it still occurs on Qt5.15.
    It would occur sometimes when a user session changes, e.g., user login or logout (but I don't know exactly which moment ).

    JonBJ Offline
    JonBJ Offline
    JonB
    wrote on last edited by JonB
    #2

    @sjlee said in a SIGSEGV in Linux:

    a user session changes, e.g., user login or logout

    Qt, as a C++ library, does not have any "user session" or "user login or logout", so what does this mean?

    S 1 Reply Last reply
    0
    • JonBJ JonB

      @sjlee said in a SIGSEGV in Linux:

      a user session changes, e.g., user login or logout

      Qt, as a C++ library, does not have any "user session" or "user login or logout", so what does this mean?

      S Offline
      S Offline
      sjlee
      wrote on last edited by sjlee
      #3

      @JonB
      Hi, Regarding the terms, please refer to this site: https://www.freedesktop.org/software/systemd/man/org.freedesktop.login1.html

      Thank you.

      JonBJ 1 Reply Last reply
      0
      • S sjlee

        @JonB
        Hi, Regarding the terms, please refer to this site: https://www.freedesktop.org/software/systemd/man/org.freedesktop.login1.html

        Thank you.

        JonBJ Offline
        JonBJ Offline
        JonB
        wrote on last edited by JonB
        #4

        @sjlee
        I have absolutely no idea how that interacts/changes with your running Qt application, about which you say nothing. Perhaps somebody else does.

        1 Reply Last reply
        0
        • S sjlee

          Hello,

          I have a SIGSEGV crash in Qt. Could you please tell me what the crash is? Thanks in advance.

          Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f070370c9f6 in __run_exit_handlers (status=1, 
    listp=0x7f07038ae718 <__exit_funcs>, 
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true)
    at exit.c:77
77	exit.c: No such file or directory.
[Current thread is 1 (Thread 0x7f070281e700 (LWP 4848))]
(gdb) 
(gdb) 
(gdb) bt
#0  0x00007f070370c9f6 in __run_exit_handlers (status=1, 
    listp=0x7f07038ae718 <__exit_funcs>, 
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true)
    at exit.c:77
#1  0x00007f070370cbe0 in __GI_exit (status=<optimized out>) at exit.c:139
#2  0x00007f0700aca371 in QXcbConnection::processXcbEvents(QFlags<QEventLoop::ProcessEventsFlag>) [clone .cold] () from /usr/local/bin/across/libQt5XcbQpa.so.5
#3  0x00007f0700af8de3 in xcbSourceDispatch(_GSource*, int (*)(void*), void*)
    () from /usr/local/bin/across/libQt5XcbQpa.so.5
#4  0x00007f07031b417d in g_main_context_dispatch ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5  0x00007f07031b4400 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#6  0x00007f07031b44a3 in g_main_context_iteration ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#7  0x00007f07043522fe in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/local/bin/across/libQt5Core.so.5
#8  0x00007f07042fd20b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/local/bin/across/libQt5Core.so.5
#9  0x00007f0704304ade in QCoreApplication::exec() ()
   from /usr/local/bin/across/libQt5Core.so.5
#10 0x000000000056adf9 in Across::RunCommonRoutine(int&, char**, _ACROSS_CONTEXT*, __sigset_t const*, int&)::{lambda()#3}::operator()() const ()
#11 0x00007f0703ce9240 in std::execute_native_thread_routine (__p=0x1690b70)
--Type <RET> for more, q to quit, c to continue without paging--
   /var/tmp/sayongza/gcc-9.3.0_source/gcc-9.3.0/libstdc++-v3/src/c++11/thread.cc:80
#12 0x00007f070404d609 in start_thread (arg=<optimized out>) at pthread_create.c:477
#13 0x00007f07037e5293 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

          The backtrace is for Qt5.14.2 and it still occurs on Qt5.15.
          It would occur sometimes when a user session changes, e.g., user login or logout (but I don't know exactly which moment ).

          Q Offline
          Q Offline
          Qt embedded developer
          wrote on last edited by
          #5

          @sjlee said in a SIGSEGV in Linux:

          exit.c:139

          may be this line cause crash in your code.

          S 1 Reply Last reply
          0
          • S sjlee

            Hello,

            I have a SIGSEGV crash in Qt. Could you please tell me what the crash is? Thanks in advance.

            Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f070370c9f6 in __run_exit_handlers (status=1, 
    listp=0x7f07038ae718 <__exit_funcs>, 
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true)
    at exit.c:77
77	exit.c: No such file or directory.
[Current thread is 1 (Thread 0x7f070281e700 (LWP 4848))]
(gdb) 
(gdb) 
(gdb) bt
#0  0x00007f070370c9f6 in __run_exit_handlers (status=1, 
    listp=0x7f07038ae718 <__exit_funcs>, 
    run_list_atexit=run_list_atexit@entry=true, run_dtors=run_dtors@entry=true)
    at exit.c:77
#1  0x00007f070370cbe0 in __GI_exit (status=<optimized out>) at exit.c:139
#2  0x00007f0700aca371 in QXcbConnection::processXcbEvents(QFlags<QEventLoop::ProcessEventsFlag>) [clone .cold] () from /usr/local/bin/across/libQt5XcbQpa.so.5
#3  0x00007f0700af8de3 in xcbSourceDispatch(_GSource*, int (*)(void*), void*)
    () from /usr/local/bin/across/libQt5XcbQpa.so.5
#4  0x00007f07031b417d in g_main_context_dispatch ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5  0x00007f07031b4400 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#6  0x00007f07031b44a3 in g_main_context_iteration ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#7  0x00007f07043522fe in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/local/bin/across/libQt5Core.so.5
#8  0x00007f07042fd20b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/local/bin/across/libQt5Core.so.5
#9  0x00007f0704304ade in QCoreApplication::exec() ()
   from /usr/local/bin/across/libQt5Core.so.5
#10 0x000000000056adf9 in Across::RunCommonRoutine(int&, char**, _ACROSS_CONTEXT*, __sigset_t const*, int&)::{lambda()#3}::operator()() const ()
#11 0x00007f0703ce9240 in std::execute_native_thread_routine (__p=0x1690b70)
--Type <RET> for more, q to quit, c to continue without paging--
   /var/tmp/sayongza/gcc-9.3.0_source/gcc-9.3.0/libstdc++-v3/src/c++11/thread.cc:80
#12 0x00007f070404d609 in start_thread (arg=<optimized out>) at pthread_create.c:477
#13 0x00007f07037e5293 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

            The backtrace is for Qt5.14.2 and it still occurs on Qt5.15.
            It would occur sometimes when a user session changes, e.g., user login or logout (but I don't know exactly which moment ).

            JonBJ Offline
            JonBJ Offline
            JonB
            wrote on last edited by
            #6

            @sjlee
            BTW, if it helps any. It looks like there is an Xcb event causing process exit. When a C program exits there is an _atexit() function which is called during program to place a list of functions to call when the C program exits. I imagine C++ leverages something like this to place a bunch of destructor calls in a list. And somewhere in processing this list, or calling the functions on it, you are getting a SIGSEGV. It is not clear how detailed the debugger is in pinpointing exactly where. Maybe, for example, it's a double-destruction, or the object to be destructed has already been destroyed, or something of that ilk?

            I don't know what you are supposed to do with this information, but there you are :)

            S 1 Reply Last reply
            0
            • JonBJ JonB

              @sjlee
              BTW, if it helps any. It looks like there is an Xcb event causing process exit. When a C program exits there is an _atexit() function which is called during program to place a list of functions to call when the C program exits. I imagine C++ leverages something like this to place a bunch of destructor calls in a list. And somewhere in processing this list, or calling the functions on it, you are getting a SIGSEGV. It is not clear how detailed the debugger is in pinpointing exactly where. Maybe, for example, it's a double-destruction, or the object to be destructed has already been destroyed, or something of that ilk?

              I don't know what you are supposed to do with this information, but there you are :)

              S Offline
              S Offline
              sjlee
              wrote on last edited by sjlee
              #7
              This post is deleted!
              1 Reply Last reply
              0
              • Q Qt embedded developer

                @sjlee said in a SIGSEGV in Linux:

                exit.c:139

                may be this line cause crash in your code.

                S Offline
                S Offline
                sjlee
                wrote on last edited by
                #8

                @Qt-embedded-developer

                Thanks for the answer. Our app source code doesn't have exit.c. Maybe Qt or its calling library would have it.

                C 1 Reply Last reply
                0
                • S sjlee

                  @Qt-embedded-developer

                  Thanks for the answer. Our app source code doesn't have exit.c. Maybe Qt or its calling library would have it.

                  C Offline
                  C Offline
                  ChrisW67
                  wrote on last edited by
                  #9

                  @sjlee "exit.c" is quite likely the source file that implements the standard C library exit(). Is Across::RunCommonRoutine() one of yours? It seems to be the only thing outside Qt/Standard library/OS to touch that trace.

                  1 Reply Last reply
                  0
                  • S Offline
                    S Offline
                    sjlee
                    wrote on last edited by sjlee
                    #10
                    This post is deleted!
                    S 1 Reply Last reply
                    0
                    • S sjlee

                      This post is deleted!

                      S Offline
                      S Offline
                      sjlee
                      wrote on last edited by
                      #11
                      This post is deleted!
                      1 Reply Last reply
                      0
                      • S Offline
                        S Offline
                        sjlee
                        wrote on last edited by
                        #12
                        This post is deleted!
                        1 Reply Last reply
                        0
                        • Kent-DorfmanK Offline
                          Kent-DorfmanK Offline
                          Kent-Dorfman
                          wrote on last edited by
                          #13

                          When I see something like this the first thing that comes to mind is that interdependent object destructors are being destroyed in the wrong order.

                          The dystopian literature that served as a warning in my youth has become an instruction manual in my elder years.

                          1 Reply Last reply
                          0
                          • S Offline
                            S Offline
                            sjlee
                            wrote on last edited by sjlee
                            #14

                            Found the source of the crash.

                            void QXcbConnection::processXcbEvents(QEventLoop::ProcessEventsFlags flags)
{
    int connection_error = xcb_connection_has_error(xcb_connection());
    if (connection_error) {
        qWarning("The X11 connection broke (error %d). Did the X11 server die?", connection_error);
        exit(1); <= HERE
    }

                            In my app, Qt runs in a child thread and when it meets the exit(1), the standard cleanup proceeds. But my app is multi-threaded...

                            Thank you everyone for your help.

                            1 Reply Last reply
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                            • S sjlee has marked this topic as solved on

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